Equipment design features

According to the performance characteristics of graphite materials, when designing impermeable graphite chemical equipment (hereinafter referred to as graphite equipment), the following characteristics should be paid attention to:

① The high compressive strength of graphite materials should be used as much as possible. Keep the graphite components in a state of compressive stress to avoid or reduce tensile stress and bending stress;

②The channel direction of the heat exchanger must conform to the best heat conduction direction brought by graphite anisotropy. Because the thermal conductivity of graphite products perpendicular to the direction of the extrusion axis is 25% smaller than the direction parallel to the axis, when designing the heat transfer element, the direction of heat transfer and heat flow should be as far as possible along the axis of the graphite extrusion;

③As heating equipment, when resin-impregnated graphite, pressed graphite and its cement are used in combination with metal materials or other materials to manufacture heating equipment, the difference in thermal expansion coefficient will cause excessive temperature stress, so the use of adhesive should be minimized.接结构。 Connected structure. When designing the tubular heat exchanger, it is especially necessary to select materials and structural forms reasonably;

④The main graphite parts of the equipment should also try to avoid using structures with bonding seams. Due to the different thermal expansion coefficients of the cement and graphite materials, the bonding seam will produce temperature stress at a higher operating temperature, and it may cause embrittlement and break the parts under the action of the medium temperature and time effect. At present, the maximum size of artificial graphite blanks used in manufacturing equipment in my country: square cross-section is 400mm X 400mm, cylindrical cross-section is generally φ40Omm, the maximum is φ1800mm, and the required graphite parts often exceed the maximum size of graphite blanks. At this time, an adhesive structure is inevitably required. At this time, the gluing seam of graphite parts should be tight and uniform, and the width of the seam is generally not more than 1mm;

⑤Connecting parts of metal materials, such as bolts and studs, should not be screwed directly on the graphite element;

⑥ The geometry of the parts and the equipment structure should not be too complicated;

⑦The graphite nozzle should not be too long to extend out of the outer wall of the equipment to avoid damage during transportation or use;

⑧The hoisting position of the equipment should be considered, and it is generally not suitable to hoist directly on impermeable graphite components;

⑨Due to the heterogeneity of graphite materials, a larger safety factor is used in the strength calculation, which is generally 9-10 (the former West German AD standard N2 is 9 and Japan usually takes 10. The basic materials and process guarantee conditions are very good. When, consider choosing n=9).

Manufacturing process

The processing and manufacturing process of impermeable graphite equipment and its components varies with the structure of the equipment. The machinability of impermeable graphite is similar to that of cast iron. It has a lower hardness than cast iron. It can be added with metal cutting tools or woodworking tools. Such as turning, planing, milling, drilling, sawing, grinding and other processing. Because graphite itself has poor strength and brittleness. Generally, two dipping and two adding methods are used to improve its strength and ensure processing accuracy.

The processing and manufacturing of impermeable graphite equipment shall comply with the "Technical Conditions for Graphite Chemicals" (HG 2370) and other relevant standards to strictly control all construction links to ensure construction quality.

The graphite material is hard but brittle, and it is very easy to break. Therefore, graphite materials and any components and products should be handled with care during any handling, and it is strictly forbidden to throw them around. In the machining process, when clamping is required, the force must be even. Avoid local excessive force. In the machining and assembly process. It is strictly forbidden to hit with a golden hammer. When hitting is necessary, a mallet covered with rubber should be used.

Nevertheless, the overall level of my country's graphite equipment industry is not high, because most of the current main materials for making graphite equipment are still graphite electrodes, and there are not many varieties of leaching agents. The internal structure of the graphite electrode has coarse particles (the particle size is about 6-10mm). The porosity is high (usually around 20%) and the mechanical properties are poor, resulting in poor performance and quality of graphite equipment. Therefore, how to develop special graphite for chemical industry, improve the mechanical and physical properties of graphite materials, develop new varieties of high-performance impregnants, and improve the processing and manufacturing technology of graphite equipment, thereby improving the performance and quality of graphite equipment, is the goal and focus of our future work.